The present invention relates to mobile phone, and particularly relates to a mobile phone for controlling a sending power in accordance with an instruction applied from a base station.
Conventionally, a sending power of a mobile phone is controlled to take an optimum value in accordance with a position and others of the mobile phone so that communication with a base station can be performed without impeding communication between other mobile phones and base stations. Further, the maximum sending power is restricted not to exceed a predetermined value (e.g., 25 dBm).
The sending power of mobile phone is controlled in two stages for open loop control and inner loop control. In the open loop control, the mobile phone calculates a required sending power based on a receiving power, and starts sending with the calculated power. In the inner loop control, the base station gives the mobile phone an instruction for increasing or decreasing the sending power in accordance with changes in position of the mobile phone and others. In the inner loop control, the sending power is also increased or decreased for reasons on the mobile phone side (e.g., DTX).
FIG. 8 is a flowchart representing inner loop control of a conventional mobile phone. In FIG. 8, a mobile phone calculates a power control amount xcex94P in a step S51 based on, e.g., signals sent from a base station, and detects a sending power Px of a current or present slot in a step S5 for determining in a step S53 whether sending power Px is equal to or smaller than a predetermined threshold power Plim or not. When it is determined in step S53 that sending power Px is equal to or smaller than predetermined threshold power Plim, the sending power of the next slot is increased or decreased by xcex94P in a step S54. When it is determined in step S53 that sending power Px is larger than predetermined threshold power Plim, the power control is not performed.
FIG. 9 is a time chart representing by way of example the inner loop control of the mobile phone already described with reference to FIG. 8. In FIG. 9, an allowed maximum sending power is in a range Pmaxr from 21 dBm to 25 dBm, a maximum sending power Pmax is equal to 25 dBm, and threshold power Plim is set to 23 dBm. FIG. 9 represents a case where a mobile phone receives an instruction for every slot from a base station to increase the sending power by 1 dB. When sending power Px exceeds threshold power Plim of 23 dBm, the mobile phone does not increase the sending power even if the base station provides the instruction to increase the sending power. This prevents sending power Px from exceeding maximum sending power Pmax.
In the case shown in FIG. 9, no problem occurs as long as the base station instructs the mobile phone to increase sending power Px by 1 dB or 2 dB. However, sending power Px will exceed maximum sending power Pmax when an instruction for increasing sending power Px by 3 dB or more is provided. Alternatively, if threshold power Plim is set to a low value, it is possible to prevent sending power Px from exceeding maximum sending power Pmax. However, this reduces a communication-allowed range because sending power Px is set to a lower value.
Accordingly, a major object of the invention is to provide a mobile phone, which has a sending power not exceeding a maximum sending power, and also has a large communication-allowed range.
For achieving the above object, the invention provides a mobile phone including a receiving portion for receiving a signal from a base station; a sending portion capable of control of a sending power for sending a signal to the base station; a power calculating portion for determining a power increase amount of a next slot based on a power control command or the like applied from the base station via the receiving portion; a determining portion for obtaining a first sum of the sending power of a current slot and the power increase amount determined by the power calculating portion, and determining whether the first sum is smaller than a predetermined maximum sending power or not; and a power control portion for increasing the sending power of the next slot of the sending portion by the power increase amount obtained by the power calculating portion when the determining portion determines that the first sum is smaller than the maximum sending power, and for calculating the power increase amount providing the sending power of the sending portion not exceeding the maximum sending power, and increasing the sending power of the next slot of said sending portion by the calculated power increase amount when the determining portion determines that the first sum exceeds the maximum sending power.
As a major advantage of the invention, when it is determined that the sending power will exceed the maximum sending power if the sending power is increased by the power increase amount determined based on, e.g., power control commands applied from the base station, the calculation is made to provide the sending power not exceeding the maximum sending power, and the sending power is increased only by the calculated power increase amount. Therefore, the sending power does not exceed the maximum sending power. The sending power can be equal to the maximum sending power when necessary. This increases a communication-allowed range as compared with a conventional structure, in which the set sending power is relatively low.
Preferably, the sending portion includes a variable gain amplifier/attenuator for amplifying or attenuating a send signal with a gain according to a control signal. The mobile phone further includes a storage portion for storing a table or a function representing a relationship between the control signal and the sending power of the sending portion. The power control portion controls the sending power of the sending portion by applying the control signal to the variable gain amplifier/attenuator based on the table or function stored in the storage portion. This structure allows each control of the sending power.
More preferably, the mobile phone includes a power detecting portion for detecting the sending power of the sending portion, and the sending power of the current slot used in the determining portion is detected by the power detecting portion.
Preferably, the power detecting portion has a predetermined power detection range, and a lower limit of the power detection range is set to a value lower than the maximum sending power by a value equal to or larger than a maximum value of the power increase amount obtained by the power calculating portion. The power control portion increases the sending power of the sending portion by the power increase amount determined by the power calculating portion independently of results of determination of the determining portion when the sending power of the sending portion is outside the power detection range of the power detecting portion. This can reduce the power detection range of the power detecting portion so that the detection accuracy of the power detecting portion can be improved, and the structure can be simplified.
Preferably, the power detecting portion has a predetermined power detection range. When the sending power of the sending portion is outside the power detection range of the power detecting portion, the determining portion obtains a second sum of the sending power of the sending portion determined from the control signal, a maximum value of an error in the sending power and the power increase amount of the next slot obtained by the power calculating portion, and determines whether the second sum is smaller than the maximum sending power or not. The power control portion increases the sending power of the sending portion by the power increase amount obtained by the power calculating portion when the second sum is smaller than the maximum sending power according to the determination of the determining portion. The power control portion calculates the power increase amount providing the sending power of the sending portion not exceeding the maximum sending power, and increases the sending power of the sending portion by the calculated power increase amount when the second sum is larger than the maximum sending power according to the determination of the determining portion. This structure can further reduce the power detection range of the power detecting portion so that the detection accuracy of the power detecting portion can be further improved, and the structure can be further simplified.
Preferably, the mobile phone further includes a temperature detecting portion for detecting a temperature of the power detecting portion, and a first correcting portion for correcting a detected value of the power detecting portion based on the results of detection of the temperature detecting portion.
More preferably, the mobile phone further includes a frequency detecting portion for detecting a send frequency of the sending portion, and a second correcting portion for correcting the detected value of the power detecting portion based on the results of detection of the frequency detecting portion.